Organizational factors associated with variation in primary care providers in ACOs.

Objective:  To assess the association between the organizational structure of accountable care organizations (ACOs) and provider workforce composition. Quantifying these relationships may improve understanding of factors contributing to changes in the health care workforce in ACOs and improve clinician recruitment and retention across ACOs to help them succeed in the program.

Study design: Cross-sectional study of 409 ACOs from the National Survey of Accountable Care Organizations Wave 4 (2017-2018; response rate, 48%).

Methods: We evaluated ACO provider workforce composition. In multivariable linear regression models, we examined the relationship among ACO provider workforce composition, contract type, structure, and financial risk level. For Medicare Shared Savings Program participants, we also assessed the role of the market environment.

Results:  We found that provider workforce composition varied across organizations by ACO contract payer. The percentage of primary care providers-physicians and nonphysician providers-was higher in smaller organizations with ACO contracts from a single public payer (77.7% for those with Medicaid-only contracts; 59.5% with Medicare-only contracts) relative to larger organizations with contracts from a single commercial payer (52.4% primary care providers) or multiple payers (54.8%-55.7%). A higher percentage of primary care providers in the ACO was associated with physician leadership, upside financial risk, and financial compensation of physicians being tied to performance measures.

Conclusions: With payers' recent interest in more capitated payment models, larger ACOs should consider extending more population-based payments, provider engagement, and compensation strategies to engage aligned providers toward high quality and low costs, mitigate overall provider turnover, and make participation in ACOs sustainable.